A number of vaccine strategies for prevention of AIDS have been proposed, including use of attenuated bacterial and viral vectors expressing various epitopes from HIV, hybrid hepatitis particles expressing a VC loop peptide, DNA vaccines expressing gp120, and synthetic peptides containing B- and T-cell epitopes of HIV as immunogens. HIV subunits (gp120, gp160) and whole killed HIV have been tested in humans and non-human primates. None of these has been effective. A major problem limiting the development of an effective HIV vaccine is that the immune correlates of protection against HIV are not known. In this proposal, the applicants address a new strategy for prevention of AIDS by vaccination. They have developed a novel mucosal adjuvant which has been shown in numerous animal studies to induce protective immunity when coadministered with whole inactivated bacteria or viruses, or subunits or relevant virulence determinants from these pathogens. This adjuvant promotes the development of both antigen- specific humoral(antibody) and cell-mediated immune responses against the pathogen in both the systematic and mucosal compartments. In addition, the adjuvant has recently undergone two Phase I clinical studies in humans and has been shown to be safe and nontoxic at adjuvant-effective doses. The proposed studies will focus on the use of this adjuvant for production of humoral and cell-mediated immune responses against a model of HIV antigen - gp120. The main goal of this study is to characterize the humoral and cellular response against HIV gp120 when administered with the adjuvant, and to determine whether the nature of the humoral or cellular immune responses to this antigen when delivered in the presence or absence of this adjuvant will be influence by the route of immunization, or the number of doses administered. Since the immune protective correlates to HIV infection are unknown, the type of immune response induced by vaccination will be characterized in depth. Serum and mucosal anti-gp120 antibodies will be determined and characterized with respect to antigen-specific Ig isotypes and distribution in serum and mucosal secretions by ELISA and Western blot, and the ability to neutralize HIV infectivity in vitro. Cellular studies will be applied to determine the type of T helper cell response induced and the cytokine profile during the effector phases of the immune response, with special regard to development of TH1 and TH1 type response, as well as CTL activity.